The invention generally relates to a circuit to indicate the status of a supply voltage.
A typical computer system includes a power supply that provides and regulates various supply voltages that are used by the components of the computer system. As examples, the computer system may provide and regulate supply voltages for 5 volt (V), 3.3 V, 2.5 V, 1.8 V and 1.5 V supply lines, or power planes, of the computer system.
One component that receives supply voltages from the voltage planes of the system is a microprocessor. The microprocessor may be encoded with a voltage identification (VID) number, a number that identifies a specific supply voltage to be furnished to the core circuitry of the microprocessor. In this manner, at powerup of the computer system, circuitry of the microprocessor other than its core circuitry may receive a supply voltage for purposes of communicating an indication of the VID number to an external voltage regulator. This voltage regulator then generates the supply voltage for the core circuitry of the microprocessor based on the indicated VID number.